Of all of the dumb things that Donald Trump said Thursday in announcing his decision to pull the United States out of the Paris climate agreement, this might well top the list:

“The Paris Climate Accord is simply the latest example of Washington entering into an agreement that disadvantages the United States, to the exclusive benefit of other countries, leaving American workers, who I love, and taxpayers to absorb the cost in terms of lost jobs, lowered wages, shuttered factories and vastly diminished economic production.”

In fact, withdrawing from the accord will likely have the opposite effect on job creation. Solar and other green energies are booming, and economists have argued that Trump’s push to prop up the fossil fuel industry could result in less investment in the clean energy sector.

“In the end, if the United States are not vigilant, all the fantastic new jobs in the renewable energies will just simply go to China and India,” United Nations Environment chief Erik Solheim told NPR.

The Paris climate deal, negotiated in 2015 and signed in 2016, was made among 195 countries to keep the Earth’s temperatures from warming more than 2 degrees celsius by reducing emission levels. 2016 was the hottest year on record, and the last three years have seen the largest temperature increase since NASA began keeping track in 1880.

Trump’s decision makes the United States the only country except Syria, which didn’t send a representative to the Paris conference, and Nicaragua, which refused to sign because the agreement didn’t go far enough, not participating in the accord.

Jamie Henn, director of strategy and communications at the climate advocacy organization 350.org, called Trump’s decision a major blow in the fight against climate change.

“This is a historic blunder and will go down as one of the worst decisions that any U.S. President has ever made,” he told The Progressive, noting that the majority of Americans support staying in the agreement.

Henn added that it’s still technically possible to meet the climate goals agreed to by then-President Barack Obama, although that will be far more difficult now. “It will require making real progress over the next four years outside of the federal government and then taking back power in 2020 with a President who’s deeply committed to a truly ambitious plan to combat climate change,” he said.

“This is a historic blunder and will go down as one of the worst decisions that any U.S. President has ever made.”

The United States produces more carbon emissions than any other country except China. When Obama signed the United States onto the agreement in the fall of 2016, he committed to lowering the country’s emissions output between 26 and 28 percent by 2025, compared to 2005 levels.

While Trump can’t officially pull out of the agreement until November 2020, his decision to withdraw creates serious hurdles for the goals of the accord. Minutes after Trump’s speech, France, Germany, and Italy issued a joint statement saying that the climate agreement can’t be renegotiated, “since it is a vital instrument for our planet, societies and economies.”

It is no surprise that Trump has reneged on the United States’ commitment to the deal. Trump has repeatedly called climate change a hoax and scoffs at the overwhelming body of scientific evidence that shows temperatures are rising.

“The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive,” he infamously tweeted in 2012.

The decision to pull out of the climate accord divided Trump’s White House staff. Chief Strategist Steven Bannon urged Trump to withdraw from the deal while Secretary of State Rex Tillerson and Ivanka Trump both supported staying in the accord. Tillerson and Ivanka both fell in line after Trump’s announcement, however, quietly accepting his decision.

Environmental advocacy organizations blasted Trump’s decision to back out of the accord. Michael Brune, executive director of the Sierra Club, called the announcement “a historic mistake,” adding that generations to come will look back with “stunned dismay at how a world leader could be so divorced from reality and morality.” Rhea Suh, president of the Natural Resources Defense Council, said Trump’s decision is “a reckless and foolish mistake” and that “our kids will pay the price.”

Even oil companies—such as ExxonMobil, Chevron, Royal Dutch Shell, and BP—have in the past expressed their opposition to the United States leaving the Paris agreement.

Many climate activists have previously criticized the Paris agreement for not going far enough to curb rising temperatures. Bill McKibben, co-founder and senior advisor at 350.org, said the deal gave countries too much time to transition away from fossil fuels, leaving open the possibility of “endless climate damage.”

Despite the weakness of the original deal, Trump’s withdrawal is still devastating news. Jeremy Symons, associate vice president of climate political affairs at the Environmental Defense Fund, told The Progressive that pulling out of the accord “puts our health at risk, will lose clean energy jobs, and will lead our kids to fend for themselves in a climate-changing world.”

But Symons holds out hope that Trump’s move will spur climate-related activism.

“I have no doubt that Americans are going to respond to this and the movement for action is going to strengthen,” Symons said. “The country will wake up tomorrow and realize that the responsibility for climate leadership now rest on all of our shoulders.”